Molecular Sieve

The molecular sieve is a crystal aluminosilicate. With the uniform pore size and great specific surface area, it is provided with as many outstanding advantages as listed below:

 

1.The selective adsorption according to the different molecular size and shape, i.e. to adsorb the molecules smaller than the pore size of molecular sieve only; The selective adsorption of small polar molecules and unsaturated molecules, and its selective adsorbability is greater in case of the greater polarity and unsaturation;

 

 

2. The enormous water absorption. It maintains a high water absorbing capacity even at a high temperature, high air velocity and lower water content.

 

Now the products that have been put into production for industrial use mainly include 3A, 4A, 5A, 10X, 13X and copper molecular sieves.

 

1.  3A Molecular Sieve

(1) Product Description

Usually the pyrolysis gas contains 400 to 700 PPm moisture that will be frozen in cryogenic separation, and at a high pressure and low temperature, the white crystal of hydrocarbon mixture will be generated from water and low carbon paraffin hydrocarbon (e.g. CH₄, C₂H₆ and C₃H₈, etc.). In addition, the crystal of ice and hydrocarbon mixture will also lead to the blocking of pipeline or equipment, resulting in the shutoff of the system. In such a case, the petroleum pyrolysis gas must be deeply dehydrated and dried prior to the cryogenic separation so that the moisture in pyrolysis gas could be reduced to less than 5 PPm (i.e. its dew point is lower than TMP -60 ). Now, the best deep drying adsorbent that is commonly used and generally recognized at home and abroad is 3A zeolite molecular sieve. Since it adsorbs only the moisture present in pyrolysis gas and not the larger hydrocarbon molecules (e.g. C₂H₆, C₂H₄,C₃H₈ and C₃H₆ etc.), it can prevent the coking of olefin compound within the pore canal of molecular sieve and prolong the service life of adsorbent.

 

(2) Main Technical Conditions of 3A Strip Molecular Sieve

 

(3)Technical Conditions of 3A Spherical Molecular Sieve

(4) Typical applications:

● Dehydration of many kinds of liquids (say ethanol).

● Dehydration of air.

● Dehydration of refrigerant.

● Dehydration of natural gas or methane.

● Dehydration of cracked gas ,ethylene , propylene or butadiene.

 

 

2.  4A Molecular Sieve

 

(1) Introduction
Lihua Molecular Sieve type 4A is an alkali alumina silicate; it is the sodium form of the Type A crystal structure. 4A molecular sieve has an effective pore opening of about 4 angstroms (0.4nm). Lihua type 4A molecular sieve will adsorb most molecules with a kinetic diameter of less than 4 angstroms and exclude those larger. Such absorbable molecules include simple gas molecules such as oxygen, nitrogen, carbon dioxide and straight chain hydrocarbons. Branched chain hydrocarbons and aromatics are excluded.

 
 Typical Chemical Formula
 Na2O . Al2O3 . 2SiO2 . 4.5 H2O
 SiO2 : Al2O3 ≈2

 

(2)Technical Parameter

 

(3)Application
 ·Drying and removing of CO2 from natural gas, LPG, air, inert and atmospheric gases, etc.
 ·Removal of hydrocarbons, ammonia and methanol from gas streams (ammonia sync gas treating)

 ·Special types are used in the air break units of buses, trucks and locomotives.
 ·Packed in small bags, it may be used simply as a packaging desiccant.
 

(4)Regeneration

Lihua molecular sieve Type 4A can be regenerated by either heating in the case of thermal swing processes;

or by lowering the pressure in the case of pressure swing processes.
To remove moisture from a 4A molecular sieve, a temperature of 250-280°C is required. A properly regenerated molecular sieve can give moisture dew points below -100°C.
The outlet concentrations on a pressure swing process will depend on the gas present, and on the conditions of the process

 

 (5)Size
4A - Zeolites are available in beads of 1-2 mm, (10x18 mesh) 2-3 mm, (8x12 mesh) , 2.5-5 mm, (4x8 mesh) and as powder, and in pellet 1.6”, 3.2”.

 

 (6)Attention
 To avoid damp and pre-adsorption of organic before running, or must to be reactivated.

 

 

3.  5A Molecular Sieve

(1) Product Description

An alkali alumina silicate, it is the calcium form of the Type A crystal structure. Type 5A has an effective pore opening of 5 angstroms (0.5 nm). It will adsorb molecules with a kinetic diameter of less than 5 Angstrom and exclude those larger.
Typical Chemical Formula
0.70CaO 0.30Na2O Al2O3 2.0SiO2 4.5H2O

SiO2: Al2O3 ≈2

 (2)Technical Parameter

 

(3)Application:
 ·Remove water, CO2, H2S from sour natural gas streams, while minimizing COS formation. Light mercaptans are also adsorbed.
· Used for the separation of normal- and iso paraffin(C4 to C6 species). 
· Production of high purity N2, O2, H2 and inert gases from mixed gas streams.

 
(4) Regeneration 
Either heating in the case of thermal swing processes, or by lowering the pressure in the case of pressure swing processes. To remove moisture from temperature of 250-300°C. Properly can give moisture dew points below -100°C, or merchantman or CO2 levels below 2 ppm v.

 

4.  5A De-waxing Molecular Sieve

(1) Product Description

Application: Extensively applied in the separation of normal paraffin hydrocarbon (de-waxing) in petroleum and its distillate. The de-waxed petroleum products are of the superior property similar with aviation kerosene at a low freezing point, and the separated normal paraffin hydrocarbon (paraffin wax) can be supplied as the chemical material of synthetic detergent.

 

(2) Main Technical Index

size Index Item		Bulk densityg g/ml >=	Static water sorption % >=	Crushing strength,N/mm2/particle >=	Abrasion ratio, %	n-Hexane sorption, (P/ps=0.1% <=	Water content in package, % <=
Strip	3~5mm	0.60	21	22	0.55	12.0	1.5
ball	4~6mm	0.62	21	60	0.50	12.0	1.5

 

5.  13X Molecular Sieve

(1) Product Description

Application: For the desulfurization (H2S, SO2, mercaptan and thiophene) of petroleum gas and natural gas, and it is also a good drying agent.

 

(2) Main Technical Index

 

(3) Typical applications:

● Purification and removal of H₂O and CO₂ .

● Dehydration and desulfuration of nature gas , liquid petrol gas and liquid alkane.

● Deep dry of common gases.

 

(4) Note:

 φ1.5 to 1.7 mm strip molecular sieve means the sample with a strip length of 1 to 6 mm as its nominal length;

φ3.0 to 3.3 mm strip molecular sieve means the sample with a strip length of 2 to 9 mm as its nominal length.

  

6.13X Air-separating Molecular Sieve

(1) Product Description

Application: For an extremely high efficient purification of unstripped oxygen and nitrogen in the air in the air separation industry, able to thoroughly eliminate the small amount of CO₂ and H₂O in the air which affects the oxygen and nitrogen separation, it is a special adsorbent necessary in the air separation industry.

 

(2) Main Technical Index

 

7.  Cu-13X Molecular sieve

Application: Mainly used to eliminate the minute amount of organic sulfur (thiaalcohol) in aviation kerosene.

Main Technical Index

 

The Cu-13X molecular sieve can be used in the desulfurization of aviation kerosene under the following technological conditions:

The temperature is higher than 130℃;

2 to 3 Kg/cm2 in pressure;

4 h-1 at air velocity.

 

Note:

(1)The nominal length of φ1.5 to 1.7 mm strip molecular sieve is 4 to 12 mm;

The nominal length of φ3.0 to 3.3 mm strip molecular sieve is 6 to 14 mm.

(2)The water content in package refers to that before delivery from manufacturer.

 

8.  10X Molecular Sieve

Application: Mainly used in the adsorption and separation of aromatic hydrocarbon and refining of paraffin wax.

 

 

Main technical Index

 

Recycling Conditions of Molecular sieve

250 to 320℃at inlet temperature of adsorption tower, greater than or equal to 150℃at outlet temperature of adsorption tower;

The recycled gas must be dry and free from the components to be adsorbed by molecular sieve (the dry nitrogen is recommended);

The duration of regeneration is only 3 to 4 hours at a constant temperature;

The recycled gas is often used to cool down the bed for a standby use.

  

Ordering Information

The molecular sieve is of great absorptive. To keep it in a dry place and avoid exposure to the air. In case of the occurrence of moisture absorption due to a long-term storage, to recycle before used and its property won’t be

changed;

It is recommended to use the solution of PH=7 or 11 in case of A or X type molecular sieve, and the operating temperature should not exceed 600℃, otherwise it will lose its activity;

The Corporation would like to manufacture the special molecular sieve to the request of user;

If the user encounters the possible difficulties in operation, the Corporation may dispatch the technical personnel for a on-the-spot service.